Astrocytes, non-neuronal cells in the brain, are in intimate structural relationship with synaptic contacts and are emerging as active players in the development, function and plasticity of synapses. Impairments in astrocytes are increasingly implicated in multiple brain disorders with cognitive impairments including autism and schizophrenia and therefore might be contributing to the synaptic impairments in these neurodevelopmental disorders. The goal of this proposal is to fill the gap on the role of astrocyti signaling in molecular and structural synaptic remodeling during development and learning. Here, we will test the hypothesis that activity in astrocyte processes surrounding dendritic spines leads to maturation and stabilization of dendritic spines during development and learning. To test the hypothesis, we will combine in vivo imaging of dendritic spines with astrocytic calcium during development and learning in conditions with altered astrocytic calcium signaling.